Power conversion device and heat pump device

Abstract

A power conversion device (100) comprises: a rectifier (3) which is a converter for rectifying AC power supplied from an AC power supply (1) and supplying the AC power to a load (5); and a control unit (7) for controlling the load (5) so that a variation amount of current at the time of pulsation of the current flowing to the load (5) is not more than a predetermined value.

Description

[Technical field]

[0001] The present disclosure relates to a power conversion device and a heat pump device using the power conversion device. [Background technology]

[0002] In controlling electric motors that drive single rotary compressors or twin rotary compressors that are applied to heat pump devices such as air conditioners and refrigerators, there is a technique for suppressing an increase in power consumption by appropriately compensating for the torque pulsation component according to the state of the electric motor (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-178814 A Summary of the Invention [Problem to be solved by the invention]

[0004] The motor control device described in Patent Document 1 controls a motor that drives a load whose load torque pulsates periodically. However, in the case of a power conversion device that converts AC power supplied from an AC power source into DC power and supplies it to a load, if the load torque pulsates at a frequency asynchronous with the power source frequency, the charge / discharge current flowing from a converter that converts AC to DC to a smoothing capacitor becomes unbalanced between the positive and negative of the power source voltage. As a result, there is a risk that the harmonics of the power source current will increase. Here, the upper limit of the harmonics of the power source current is set by a standard. In particular, the upper limit of even harmonics is set stricter than that of odd harmonics because they adversely affect other devices connected to the power source system. For this reason, it is necessary to suppress the harmonics of the power source current that are generated due to the influence of the pulsation of the load torque.

[0005] The present disclosure has been made in consideration of the above, and aims to provide a power conversion device capable of suppressing harmonics in a power supply current that are generated when AC power supplied from an AC power supply is rectified to generate DC power to be supplied to a load. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a power conversion device according to the present disclosure includes a converter that rectifies AC power supplied from an AC power source and supplies the rectified power to a load, a control unit that controls the load so that a fluctuation amount of a current when the current flowing through the load pulsates is equal to or less than a predetermined value, a reactor provided between the AC power source and the converter; and a capacitor provided between the converter and a load for smoothing a voltage output by the converter; Equipped with The determined value is determined based on the inductance value of the reactor, the capacitance value of the capacitor, and the limit value set by the standard for the even-order harmonic components of the current flowing from the AC power source to the converter. Effect of the Invention

[0007] The power conversion device according to the present disclosure advantageously suppresses harmonics in the power supply current that are generated when AC power supplied from an AC power supply is rectified to generate DC power to be supplied to a load. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a configuration example of a power conversion device according to a first embodiment; [Diagram 2] FIG. 1 is a diagram showing another configuration example of the power conversion device according to the first embodiment; [Diagram 3] FIG. 1 is a diagram showing an example of current and voltage waveforms when a load is operated at constant power. [Figure 4] FIG. 1 is a diagram showing an example of current and voltage waveforms when a load is operated while varying a load current Io. [Diagram 5] A diagram showing the frequency components that occur in the input current Is when the load current Io fluctuates when the frequency of the power supply voltage Vs is 50 Hz. [Figure 6] FIG. 1 is a diagram showing an example of current and voltage waveforms when a power conversion device operates a load at a constant current. [Figure 7] FIG. 13 is a diagram showing another example of current and voltage waveforms when the power conversion device operates the load while varying the load current Io. [Figure 8] A diagram showing the relationship between the combination of reactor inductance value and capacitor capacitance value of a power conversion device and the power value at which the input current Is becomes unbalanced. [Figure 9] FIG. 9 is a diagram showing the relationship between the load power and the resonant frequency shown in FIG. [Figure 10] FIG. 1 is a diagram illustrating an example of a hardware configuration for implementing a control unit included in a power conversion device according to a first embodiment. [Figure 11] FIG. 1 is a diagram showing a configuration example of a heat pump device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a power conversion device and a heat pump device according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0010] Embodiment 1 1 is a diagram illustrating a configuration example of a power conversion device according to a first embodiment. The power conversion device 100 includes a reactor 2, a rectifier 3 which is a converter, a smoothing unit 4, a load 5, a current detector 6, and a control unit 7. The power conversion device 100 is connected to an AC power source 1 and receives a supply of AC power from the AC power source 1.

[0011] The power supply voltage Vs input from the AC power supply 1 is rectified by the rectifier 3 via the reactor 2, and smoothed by being stored in the capacitors 4a and 4b constituting the smoothing unit 4 connected to the output end of the rectifier 3, before being supplied to the load 5. If the side of the output terminal of the AC power supply 1 to which the reactor 2 is connected is taken as positive, the capacitor 4a of the smoothing unit 4 is charged when the power supply voltage Vs is positive, and the capacitor 4b is charged when the power supply voltage Vs is negative.

[0012] Here, the AC power source 1 may be a commercial power source of 50 Hz or 60 Hz, or may be an AC voltage generated by a distributed power source such as a stationary storage battery or a solar power generation system.

[0013] The reactor 2 may be an EI or EE type reactor made of laminated electromagnetic steel sheets, or may use an iron core made of ferrite or amorphous material, etc. The material of the windings may be copper, aluminum, or the like.

[0014] The rectifier 3 is realized, for example, by arranging diodes in a bridge shape. Instead of diodes, the rectifier 3 may be configured by power semiconductors such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The diodes and power semiconductors such as MOSFETs may be made of general silicon materials, or may be wide band gap semiconductors with lower loss.

[0015] The capacitors 4a and 4b are aluminum electrolytic capacitors, small-capacity film capacitors, or the like.

[0016] Moreover, the rectifier 3 may be a rectifier 30 of a full-wave rectifier circuit as shown in Fig. 2. Fig. 2 is a diagram showing another configuration example of the power conversion device according to the first embodiment. The power conversion device 100a shown in Fig. 2 is obtained by replacing the rectifier 3 of the power conversion device 100 shown in Fig. 1 with the rectifier 30 configured with a full-wave rectifier circuit, and replacing the smoothing unit 4 with a smoothing unit 40 configured with a capacitor 41. As shown in Figs. 1 and 2, the power conversion device according to the first embodiment may be any device that includes a rectifier and a capacitor that smoothes the DC power after rectification.

[0017] The load 5 connected across the capacitor constituting the smoothing unit 4 can be, for example, an inverter and an electric motor, but is not limited to this. The load 5 may be any load that consumes the charge stored in a capacitor for smoothing DC power, such as an LED (Light Emitting Diode) light or an IH (Induction Heating) cooker.

[0018] 1 and 2, the power conversion device includes the load 5, but some or all of the elements constituting the load 5 may be configured to be outside the power conversion device. For example, when the load 5 includes an inverter, the power conversion device may include up to the inverter, and the remaining elements may be configured to be outside the power conversion device.

[0019] The control unit 7 generates and outputs a control signal for controlling the power or current consumed by the load 5 based on the load current Io detected by the current detector 6, i.e., the current flowing through the load 5. Note that in this embodiment, the current flowing through the load 5 is detected by the current detector 6, but the control unit 7 may estimate the load current Io based on the DC voltage Vdc applied to the load 5 and the current detected inside the load 5, for example, the value of the current flowing through a motor, instead of the detected value of the load current Io by the current detector 6, and generate a control signal using the estimated current value.

[0020] Here, waveforms when the load 5 is operated at a constant power and the power is increased are shown in Fig. 3. Fig. 3 is a diagram showing an example of current and voltage waveforms when the load 5 is operated at a constant power.

[0021] The waveforms shown in Fig. 3 indicate, from the top, the power supply voltage Vs output by the AC power supply 1, the input current Is from the AC power supply 1 to the power conversion device 100, which is a power supply current, the DC voltage Vdc supplied from the smoothing unit 4 to the load 5, and the load current Io. When the load 5 is operated at constant power, the load current Io is the power divided by the DC voltage Vdc. In other words, when the load 5 is operated at constant power, as shown in Fig. 3, the load current Io fluctuates in accordance with the pulsation of the DC voltage Vdc, and has a waveform in which an AC component is superimposed on a DC component.

[0022] Therefore, due to the fluctuation of the load current Io, the charge consumed from the capacitors 4a and 4b constituting the smoothing unit 4 becomes non-constant. When the load current Io is large, a large amount of charge is consumed from the capacitors 4a and 4b, causing the DC voltage Vdc to drop, and when the power supply voltage Vs becomes larger than the DC voltage Vdc, a charging current flows to the capacitors 4a and 4b. However, when the load current Io is small, the charge consumed from the capacitors 4a and 4b is small, and the drop in the DC voltage Vdc is suppressed. In this case, even if the power supply voltage Vs becomes larger than the DC voltage Vdc, the amount of charge to the capacitors 4a and 4b decreases, so the charging current also decreases. Therefore, as shown in FIG. 3, the waveform of the input current Is becomes irregular and is no longer synchronized with the power supply voltage Vs. This phenomenon is particularly noticeable when the average value of the load current Io is large and fluctuates greatly, or when the capacitance of the capacitors 4a and 4b is small.

[0023] When the input current Is and the power supply voltage Vs are synchronized, the input current Is is dominated by odd-order harmonic components such as 3rd, 5th, 7th, etc., with the fundamental wave being the same frequency component as the power supply voltage Vs, and even-order harmonics are only slightly generated. However, when the input current Is flows irregularly and asynchronously with the power supply voltage Vs, current components other than odd-order harmonics are generated, specifically even-order harmonics and inter-order harmonics. Inter-order harmonics are harmonics that do not fall into either the odd-order or even-order harmonics of the input current Is. For example, if the fundamental wave frequency is 50Hz, the second-order harmonic is 100Hz, and is a frequency component between 50Hz and 100Hz.

[0024] Here, the harmonic current of the input current Is, which is the power supply current, has a limit set in 61000-3-2, a standard established by JIS (Japanese Industrial Standards) and IEC (International Electrotechnical Commission). In this standard, the limit value of odd harmonics is set higher than that of even harmonics. Therefore, in the case where components other than odd harmonics are generated as described above, the even harmonics increase and tend to exceed the limit value. In addition, the method of handling interharmonics is determined in 61000-4-7, a standard established by JIS and IEC. In this standard 61000-4-7, interharmonics are grouped by frequency within a specific range and are added to adjacent odd harmonics or even harmonics. Therefore, as the number of interharmonics increases, the number of harmonics treated as odd harmonics and even harmonics increases. Therefore, the occurrence of interharmonics cannot be ignored, and it is important to suppress their occurrence.

[0025] In the example shown in FIG. 3, the charging current equivalent to the input current Is drops once every two times, so that when the power supply frequency is 50 Hz, the 25 Hz component is significantly included. In this case, the 25 Hz component, which is an interharmonic, is added to the 50 Hz component, which is the fundamental component. However, as described above, the limit value of the fundamental component is set high, so the effect of an increase in the 25 Hz component on this limit value is small. In other words, the possibility that the fundamental component will exceed the limit value as the 25 Hz component increases is low. However, the period for charging the capacitors 4a and 4b becomes longer, and the number of times charging per certain time decreases, so the charging current per time becomes larger. If the charging current per time increases, there are concerns about the effect of a decrease in inductance due to the increase in the input current Is flowing through the reactor 2, and the deterioration of losses due to an excessive current flowing through the rectifier 3. Therefore, it is necessary to control the flow of such current, that is, to prevent the charging current per time from becoming large.

[0026] As another example, consider a case where the load current Io is varied asynchronously with respect to the power supply voltage Vs, as shown in Fig. 4. Fig. 4 is a diagram showing an example of current and voltage waveforms when the load 5 is operated while varying the load current Io.

[0027] When the load current Io is made to vary asynchronously with the power supply voltage Vs, if the load current Io is small, the drop in the DC voltage Vdc is small, and the amount of charge due to the power supply voltage Vs is small, so the input current Is decreases. Also, if the power supply voltage Vs is low (close to zero) and the load current Io is large, the DC voltage Vdc drops significantly. If a positive or negative peak occurs in the power supply voltage Vs in this state, the charging current to the capacitors 4a and 4b increases, and the input current Is increases. When the fluctuation period of the load current Io and the fluctuation period of the power supply voltage Vs are different, the input current Is contains the following components. As an example, the current components contained in the input current Is when the load current Io varies asynchronously with the power supply voltage Vs when the power supply frequency is 50 Hz are shown in FIG. 5. FIG. 5 is a diagram showing frequency components generated in the input current Is when the load current Io varies when the frequency of the power supply voltage Vs is 50 Hz. It should be noted that the current component contained in the input current Is when the load current Io fluctuates asynchronously with the power supply voltage Vs when the power supply frequency is 60 Hz can also be calculated in the same manner as described below.

[0028] The frequencies (0, 5, 10, ..., 100) in the leftmost column of Fig. 5 are the frequencies of the periodically changing waveform of the load current Io (see Fig. 4), i.e., the fluctuation frequencies of the load current Io. Hereinafter, these frequencies may be referred to as the load current fluctuation frequencies.

[0029] The ranges of values ​​(75-125, 125-175, ..., 275-325) shown in the first row of Fig. 5 indicate frequency ranges and are the units for grouping the interharmonics described above. That is, in grouping according to the provisions of the above-mentioned standard 61000-4-7, the interharmonics included in each of the ranges shown in the first row of Fig. 5 are grouped together. For example, interharmonics included in the range of 75-125 Hz belong to the same group. The values ​​written in each column other than the leftmost column from the third row onwards in Fig. 5 indicate the frequencies of the interharmonics included in the input current Is.

[0030] The entries (2nd, 3rd, ..., 6th) other than the leftmost column of the second row in Fig. 5 indicate the order of harmonics of the power supply frequency and indicate where the grouped interharmonics are added. For example, the interharmonics in the column marked "2nd" (75Hz, 80Hz, ...), i.e., the interharmonics in the range of 75 to 125Hz, are added to the 2nd harmonic. Half of the interharmonics at the boundaries of the grouping ranges (125Hz, 175Hz, 225Hz, ...) are added to one of the odd harmonics and even harmonics corresponding to each of the two ranges that contain this interharmonic, and the remaining half is added to the other.

[0031] The specific current components that are generated when the load current Io is periodically changed will be described below. In the following description, the frequency (50 Hz) of the fundamental component of the power supply voltage Vs will be referred to as power supply frequency 1f, and the frequencies (100 Hz, 150 Hz, 200 Hz, ...) of the harmonic components of the power supply voltage Vs will be referred to as power supply frequency 2f, power supply frequency 3f, power supply frequency 4f, ....

[0032] Current components that occur regardless of fluctuations in the load current Io of the AC power supply 1 include current components with frequencies shown in (1) below.

[0033] (1) Power frequency 1f, power frequency 3f, power frequency 5f,…, power frequency (2n-1)f, (n=1,2,3,…)

[0034] "Power supply frequency 1f" refers to the frequency of the fundamental wave of the power supply current, and "power supply frequency (2n-1)" refers to the frequency of the 2n-1-th harmonic of the power supply current. In other words, the fundamental wave component and odd-order harmonic components are generated regardless of fluctuations in the load current Io of the AC power supply 1.

[0035] The current components occurring in the input current Is due to the influence of the fundamental component of the load current Io include the current components with the frequencies shown in (2) to (7) below. Note that "power supply frequency 3f" represents the frequency of the third harmonic of the power supply current, and "power supply frequency 5f" represents the frequency of the fifth harmonic of the power supply current.

[0036] (2) Power supply frequency 1f-{Power supply frequency 1f-|Power supply frequency 1f-load current fluctuation frequency|} (3) Power supply frequency 1f + {Power supply frequency 1f - | Power supply frequency 1f - load current fluctuation frequency |} (4) Power supply frequency 3f-{Power supply frequency 1f-|Power supply frequency 1f-load current fluctuation frequency|} (5) Power supply frequency 3f + {power supply frequency 1f - | power supply frequency 1f - load current fluctuation frequency |} (6) Power supply frequency 5f-{Power supply frequency 1f-|Power supply frequency 1f-load current fluctuation frequency|} (7) Power supply frequency 5f + {power supply frequency 1f - | power supply frequency 1f - load current fluctuation frequency |}

[0037] In addition, the current components occurring in the input current Is due to the influence of the second harmonic component of the load current Io include the current components with frequencies shown in (8) to (13) below. These are shown in parentheses in Fig. 5 (for example, "(80, 120)").

[0038] (8) Power supply frequency 1f-{Power supply frequency 1f-|Power supply frequency 1f-load current fluctuation frequency×2|} (9) Power supply frequency 1f + {Power supply frequency 1f - | Power supply frequency 1f - load current fluctuation frequency × 2 |} (10) Power supply frequency 3f-{Power supply frequency 1f-|Power supply frequency 1f-load current fluctuation frequency x 2|} (11) Power supply frequency 3f + {power supply frequency 1f - | power supply frequency 1f - load current fluctuation frequency × 2 |} (12) Power supply frequency 5f-{Power supply frequency 1f-|Power supply frequency 1f-load current fluctuation frequency x 2|} (13) Power supply frequency 5f + {power supply frequency 1f - | power supply frequency 1f - load current fluctuation frequency × 2 |}

[0039] In this way, current components other than those of the frequencies shown in (1) are generated depending on the power supply frequency and the load current fluctuation frequency, and the amount of generation increases as the fluctuation range of the load current Io becomes larger. As shown in Fig. 5, in most cases, the interharmonics between the odd and even harmonics, which are multiples of 50Hz (power supply frequency), are generated. When the grouping process defined in the above-mentioned standard 61000-4-7 is performed, for example, when the load current fluctuation frequency is 30Hz, current components with frequencies of 80Hz, 90Hz, 110Hz, and 120Hz are generated, but these are grouped into the even harmonic of 100Hz, resulting in an increase in even harmonics. Since the limit value of even harmonics is set low in the above-mentioned standard 61000-3-2, if such interharmonics grouped into the even harmonics are generated, the possibility that the even harmonics will exceed the limit value increases.

[0040] Interharmonics of the frequencies shown in (2) to (13) above do not occur when the load current fluctuation frequency becomes zero, that is, when the load current Io becomes a direct current. Therefore, if the control unit 7 controls the load 5 so that the load current Io becomes a direct current, it is clear that the imbalance of the input current Is does not occur as shown in Fig. 6, and the occurrence of interharmonics can be suppressed. Fig. 6 is a diagram showing an example of current and voltage waveforms when the power conversion device 100 operates the load 5 with a constant current.

[0041] In the case shown in FIG. 7, specifically, when the fluctuation range, which is the amount of fluctuation of the load current Io, is small, the amount of unbalance of the input current Is is also small, and the influence on the even harmonics is small. That is, the amount of inter-harmonics added to the even harmonics is reduced. The amount of unbalance also varies depending on the inductance value of the reactor 2 and the capacitance values ​​of the capacitors 4a and 4b. FIG. 7 is a diagram showing another example of current and voltage waveforms when the power conversion device 100 operates the load 5 while fluctuating the load current Io. In the example shown in FIG. 7, the amount of fluctuation of the load current Io is about 1 / 8 compared to the example shown in FIG. 4, and it can be seen that the occurrence of unbalance of the input current Is is suppressed.

[0042] Generally, the greater the inductance and capacitance, the smaller the amount of unbalance. Therefore, by designing the reactor 2 and capacitors 4a, 4b within the range where load fluctuations are tolerable based on the fluctuation frequency of the load current Io and the power supply frequency, and preventing the inductance and capacitance of these elements from becoming larger than necessary and realizing the miniaturization of the elements, it is possible to prevent the harmonic current from exceeding the limit value while reducing costs.

[0043] Here, FIG. 8 shows the analysis result of the load power at which the imbalance starts to occur depending on the capacity of the reactor 2 and the capacitors 4a and 4b when a constant power load such as a motor drive is assumed. FIG. 8 is a diagram showing the relationship between the combination of the inductance value of the reactor 2 and the capacitance value of the capacitors 4a and 4b of the power conversion device 100, and the power value at which the input current Is becomes unbalanced. In FIG. 8, "load power" represents the load power value at which the input current Is begins to become unbalanced. The input current Is begins to become unbalanced means that the amount of interharmonics generated becomes large and the harmonic current begins to exceed the limit value. As shown in FIG. 8, when the inductance value of the reactor 2 is 3 mH and the capacitance of the capacitors 4a and 4b is 1000 μF, the input current Is begins to become unbalanced when the load power becomes 500 W. In FIG. 8, "resonant frequency" represents the resonant frequency of the reactor 2 and the capacitors 4a and 4b.

[0044] As a result of analyzing the relationship between the inductance value of reactor 2 and the capacitance of capacitors 4a and 4b and the load power at which an imbalance in the input current Is begins to occur, the analysis results shown in FIG. 8 show that when the inductance value of reactor 2 is large or the capacitance value of capacitors 4a and 4b is large, the imbalance can be suppressed even if the load power increases.

[0045] Fig. 9 is a diagram showing the relationship between the load power and the resonant frequency shown in Fig. 8. Fig. 9 is a graph in which the horizontal axis represents the load power at which an imbalance in the input current Is to the power conversion device 100 occurs, and the vertical axis represents the resonant frequency of the reactor 2 and the capacitors 4a and 4b. As shown in Fig. 9, by designing the reactor 2 and the capacitors 4a and 4b so that the resonant frequency decreases as the load power increases, it is possible to suppress the imbalance in the input current Is.

[0046] In reality, these values ​​do not necessarily match due to factors such as the effects of the winding resistance and iron loss components of reactor 2, the internal resistance of capacitors 4a and 4b, the effects of wiring impedance, and the fact that the load power is not constant but fluctuates; however, as shown in FIG. 9, setting the resonant frequency of reactor 2 and capacitors 4a and 4b above 110 Hz makes it easier to induce imbalance, so setting it to 110 Hz or less makes it easier to eliminate imbalance in the input current Is.

[0047] The resonant frequency is set to 110 Hz or less and varies depending on the load power, but by controlling the load current Io to a constant value, it is possible to suppress imbalance in the input current Is even when the resonant frequency is high. Therefore, by taking into consideration the amount of fluctuation in the pulsating load current Io, the resonant frequency of the reactor 2 and the capacitors 4a and 4b, and the input current Is and setting them, it is possible to reduce the costs of the reactor 2 and the capacitors 4a and 4b.

[0048] In addition, in the motor load of conventional general single rotary compressors or twin rotary compressors, in order to suppress an increase in vibration accompanying speed fluctuations due to load torque pulsation, the torque output by the motor is made to approximately match the load torque pulsation to prevent speed fluctuations, and in addition, the motor output torque is suppressed to prevent excessive power consumption.

[0049] In this type of operation, the load current fluctuates according to the load torque, and as mentioned above, the harmonic current of the input current increases. In the case of an inverter that drives a motor, the load power is determined by the product of the mechanical angular frequency ω and the torque τ. Therefore, it is possible to control the load current Io so that it approaches a constant value by varying the mechanical angular frequency ω or the torque τ.

[0050] However, if the load current pulsation is suppressed so that the power supply harmonic current does not increase, there is a concern that the vibration of the power supply current will increase. In the case of a general motor, the power fluctuation is proportional to the load torque and inversely proportional to the moment of inertia. If the amount of fluctuation in the load current due to the fluctuation in the load torque is not acceptable, it is possible to deal with this by designing the moment of inertia to be large. By taking such measures, it is possible to achieve both the suppression of vibration and the suppression of the power supply harmonic current. That is, the control unit 7 of the power conversion device 100 controls the load 5 so that the amount of fluctuation in the load current Io is within an acceptable range, in other words, so that the amount of fluctuation in the load current Io is equal to or less than a specified value. The acceptable range is a range in which even-order harmonics affected by the generation of inter-order harmonics in the power supply current can be maintained at or below the standard limit value, and is determined in advance taking into consideration the inductance value of the reactor 2, the capacitance of the capacitors 4a and 4b, etc.

[0051] In addition, when it is difficult to achieve both harmonic current of the input current Is and motor vibration, the stability of the input current Is relative to the load power can be improved by setting the resonant frequency of the reactor 2 and capacitors 4a, 4b to 110 Hz or less as described above.

[0052] The switching frequency of the inverter that drives the air conditioner compressor is higher than the 40th harmonic, which is the power supply harmonic regulation value of 2 kHz (when the power supply frequency is 50 Hz) or 2.4 kHz (when the power supply frequency is 60 Hz). The load current in the inverter is pulsating according to the switching frequency, but this pulsating current is unlikely to be affected by the power supply harmonics. Therefore, it is sufficient to suppress the pulsating component of the load current below the frequency of the 40th harmonic, which is the power supply harmonic regulation value.

[0053] Next, a hardware configuration of the control unit 7 included in the power conversion device 100 will be described. Fig. 10 is a diagram illustrating an example of a hardware configuration realizing the control unit 7 included in the power conversion device 100 according to the first embodiment. The control unit 7 of the power conversion device 100 is realized by, for example, a processor 91 and a memory 92 illustrated in Fig. 10.

[0054] The processor 91 is a CPU (Central Processing Unit, also referred to as a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor)). The memory 92 is a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory), or the like. The memory 92 stores a program for operating as the control unit 7 of the power conversion device 100, and the control unit 7 is realized by the processor 91 reading and executing the program. The above-mentioned program stored in the memory 92 may be provided to a user or the like in a state in which it is written in a storage medium such as a CD (Compact Disc)-ROM or a DVD (Digital Versatile Disc)-ROM, or may be provided via a network.

[0055] The control unit 7 can also be realized by a dedicated processing circuit, for example, a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a circuit that combines these.

[0056] As described above, in the power conversion device 100 according to the present embodiment, the control unit 7 that controls the load 5 controls the load 5 so that the amount of fluctuation when the load current Io, which is the current flowing through the load 5, pulsates falls within a predetermined range, specifically, so that the amount of fluctuation is reduced. In this way, the power conversion device 100 can suppress the generation of harmonics in the power supply current, which can suppress harmonics in the power supply current (input current Is) that are generated when the AC power supplied from the AC power supply 1 is rectified.

[0057] Embodiment 2 The power conversion devices 100 and 100a described in the first embodiment can be applied to devices that drive a load that operates on a DC voltage.

[0058] A heat pump device will be described below as an example of a device to which the power conversion device 100 or 100a described in the first embodiment can be applied.

[0059] 11 is a diagram illustrating a configuration example of a heat pump device 200 according to the second embodiment. The heat pump device 200 according to the second embodiment includes the power conversion device 100 described in the first embodiment.

[0060] The heat pump device 200 also includes a refrigeration cycle having a configuration in which a four-way valve 902, a compressor 903 constituting a load 5 shown in FIG. 1 etc., a heat exchanger 906, an expansion valve 908, and a heat exchanger 910 are attached via refrigerant piping 912.

[0061] The compressor 903 is provided with a compression mechanism 904 that compresses the refrigerant circulating inside the refrigerant pipes 912, and a motor 905 that operates the compression mechanism 904. The motor 905 is driven by receiving a supply of electric power from the power conversion device 100.

[0062] The heat pump device 200 having such a configuration can be used in, for example, an air conditioner, a heat pump water heater, a refrigerator, a freezer, and the like.

[0063] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0064] 1 AC power source, 2 reactor, 3, 30 rectifier, 4, 40 smoothing section, 4a, 4b, 41 capacitor, 5 load, 6 current detector, 7 control section, 100, 100a power conversion device, 200 heat pump device, 902 four-way valve, 903 compressor, 904 compression mechanism, 905 motor, 906, 910 heat exchanger, 908 expansion valve, 912 refrigerant piping.

Claims

1. A converter that rectifies AC power supplied from an AC power source and supplies the rectified power to a load; a control unit that controls the load so that a fluctuation amount of the current when the current flowing through the load pulsates is equal to or less than a predetermined value; a reactor provided between the AC power supply and the converter; a capacitor provided between the converter and the load for smoothing a voltage output by the converter; Equipped with A power conversion device in which the set value is determined based on an inductance value of the reactor, a capacitance value of the capacitor, and a limit value set by a standard for even-order harmonic components of the current flowing from the AC power supply to the converter.

2. The resonant frequency of the reactor and the capacitor is set to 110 Hz or less. The power conversion device according to claim 1 .

3. A heat pump device comprising the power conversion device according to claim 1 or 2.

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